Defoaming aqueous liquids



United States Patent 3,169,929 DEFOAMING AQUEOUS LIQUIDS William F.Nekervis, Midland, and Robert A. Canute,

Mount Pleasant, Mich., assignors to The Dow Chemical Company, Midland,Mich., a corporation of Delaware No Drawing. Filed Sept. 12, 1960, Ser.No. 55,126

2 Claims. (Cl. 252-79.1)

This invention relates to defoaming and more particularly is concernedwith a method for preventing foaming in aqueous, foam-producing strongelectrolyte solutions and to such foam inhibited aqueous compositions.

In many industrial operations, the necessary utilization of certainreactant and/or process steps results in the production of hard-to-breakobjectionable foams. For example, in the photoengraving industry foamingof the conventionally used ferric chloride etching solution many timesis encountered because of the vigorous agitation employed in the etchingoperations. This foaming results in the build-up of large foam heads inthe tanks, slowing of the revolving paddles of the etching machine andeven in overflow of the foam out of ports and shaft housings of themachine.

circuit is of reduced quality, but additionally the overflow of foam outof the machine leads to general equipment corrosion problems, slipperyfloors and generally undesirable working conditions.

It is a principal object of the present invention to pro- This foamingnot only is objectionable in'that the resulting engraved plate orprinted vide a novel method for inhibiting foaming of aqueous foamproducing electrolyte solutions.

It is a further object of the present invention to provide antifoamantsfor use with foam producing basic,,neutra1 and acidic aqueouselectrolyte solutions which antifoam- 1 ants provide a short foam-breaktime and short time to give a clear solution.

It is another objectof the presentinvention to provide foam inhibitedcompositions which have a long shelf life.

It is still a further object of the present invention to provide novelfoam inhibited compositions of ferric chloride;

It is another object of the present invention to provide novelantifoaming agents for ferric chloride photoengraving solutions whichantifoamants are useful at low con-1 centr-ations and which have apleasant odor when used in such solutions.

the detailed description presented herein-- hibiting amount of a dialkylester of a dicarbo rryli c acid thereto. Particularly'useful diestersare those compounds 7 wherein the dicarboxylate anion of the acidportion of the ester is a member selected from the group consisting ofoxalate, a saturated aliphatic fatty acid dicarbogrylate These and otherobjects andadvantages will become .40

wherein the hydrocarbon chain contains from 1 to about 6 carbon atoms,an unsaturated aliphatic fatty acid dican H boxyl-ate wherein thehydrocarbon chain contains from 2 to about 6 carbon atoms and anaromatic dicarboxylate,

and, where the alcohol portion of the ester has alkyl groups containingfrom 1 to about 10 carbon atoms. M

The novel method and compositions of the instant invention are effectivein breaking and eliminating foams in aqueous electrolyte solutionscontaining up to about 50 percent or more by weight solute when theantifoaming agent is used at a minimum concentration of about 2 partsper million in the aqueous solution. Ordinarily the antifoamant will beused over a concentration range of from about 10 parts per million up tothe limit of solubility of the antifoamant in the foam producingelectro- 3,169,929 Patented Feb. 16, 1965 ice lyte. These antifoamingagents find particular utility when used with foam producing ferricchloride solutions containing up to about 45 percent or more FeCl byweight (i.e. up to about 47.5 B. at 20/4 C.) such as are used in thephotoengraving art. In this latter application the amount of the agentto be employed will range from about 5 parts per million up to thesolubility limit of the agent in the aqueous ferric chloride. (Withdiethyl phthalate, for example, this limit of solubility is about 50parts per million.)

Use of antifoamants in concentrations above the solubility limit canresult in either formation of a scum or film on the surface of thesolution or of an immiscible phase dispersed or settled within thesolution. These side effects are particularly objectionable in the photoengraving art when they appear upon use of the etching solutions. 7

However, in other areas where the appearance of such films ordispersions may not be bothersome, e.g. in the defoaming of dilute,aqueous acidic bromine solutions, foam control of from 2 to about 20percent caustic soda solution, foam inhibition of acidified and oxidizedbrine solution and the like, amounts of antifoamant in excess of theupper solubility limit of the compound in the ous solution can beutilized if desired.

The novel antifoamant compositions of the instant invention areeffective at solution temperatures up to about C. However, ordinarilythese will be used at temperatures below about 70C. and they havebeen'found to be most elfective over a temperature range of from about50 C. down to the freezing point of the solution.

. However, it has been found that if a solution containing theantifoamant has been allowed" to freeze and solidify, uponredissolution, the antifoaming agent still is effective.

In actual operation the antifoaming agent can be added to a solution atthe time of use or processing. Preferably in the case of preparedsolutions which are stored before use, the agent will be added at thetime of solution make- The following examples-will serve to illustratefurther the present invention but are notmeant to limit it' thereto.

EXAMPLE 1 A standardized foam test was developed to obtain reproducibledata on the foaming characteristics pfjaqueous electrolyte solutions.The test is divided into two parts: The first part is an Aeration Testdesigned to give an exaggerat'ed foam depth. The second part is a BottleShake Test used to determine the time for foam breaking and solutionclearing, i.e. time for foam dissipation after solution agitation isstopped. The procedures for the tests *are as follows:

Part 1.Aerati0n Test Air is'passed at a set rate, for example, 2.4liters per Part 2.-Bottle Shake Test Two hundred milliliters of testsolution are placed in a clean 16 ounce square bottle .and the bottlethen capped or sealed.

The bottle and contents are then agitated for one minute by shakingvertically in a 12 to 18 inch oscillation at a rate of two to threeshakes per second. The bottle then is put down, on a table or bench forexample, in an aqueupper face.

The results of a number of tests run with a variety of differentantifoamants at various concentration levels and using a number ofdifferent foam producing electrolyte solutions are presented in Table Iwhich follows:

In addition to the above-described quantitative measurements, inqualitative studies about parts per million of diethylphthalate werefound to satisfactorily prevent foaming of a dilute, acidic aqueousbromine solution; di-n-octyl tartrate, about 200 parts per million, wasfound both to be compatible with and an effective defoamer for a percentferric chloride etching" solution; an acidified, oxidized mixed halidesalt solution was satisfactorily defoamed by addition of about 20 partsper million diethylphthalate thereto; and, about 5 parts per milliondiethylphthalate satisfactorily prevents foaming of a 5 percent ferricchloride (about 5 B6. at 20/4 C.) solution.

Various modifications can be made in the method of the present inventionwithout departing from the spirit or scope thereof for it is understoodthat We limit ourselves only as defined in the appended claims.

We claim:

1. An aqueous ferric chloride etching solution containing a diestermember selected from the group consisting of diethyl phthalate, dibutylphthalate, dimethyl phthalate, diethyl oxalate and diethyl fumarate,said ferric chloride etching solution containing from about 5 to aboutweight percent ferric chloride and the amount of said diester memberranging from about 2 parts per million up to the solubility limit ofsaid member in said aqueous ferric chloride etching solution.

2. A composition consisting essentially of an aqueous ferric chloridesolution and containing from about 5 to about parts per million diethylphthalate, said ferric chloride solution containing from about 5 toabout 45 weight percent ferric chloride.

TABLE I Electrolyte Solution Antifoamant ii tggl Bottle Shake Test TestNo. (Height of C -1 Cone, foam and Foam Foam Solution ompos lDIl percentComposition p.p.m. solution, Height. Break time clear time solute ml.)mm. (seconds) (seconds) Series A: F 13 39 None-Control So1'n 1 100 10100 600 39 Diethylphthalate 20 600 10 3 12 40 N one-Control Soln 750 1013 40 Diethylphthalate. 10 290 5 5 40 Dlbutylphthalate 20 205 l-2 5 5 40Dlethyloxalatc-.- 1 400 210 40 Diethylfumarate 100 450 5 7 10 3+ I}N0ne-C0ntrg1 1 a o 240 FeC13+FeS04 }Dlethylphtha1ate 2 5 0 20 CausticSoda 20 None-Control Soln. 15 17 -u flc 20 Dlethylphthalate 10 2. 5 Z-3'2 39 N one-Control Soln- 1, 10 90 180 39 Diethylphthalate t 20 2. 5 6 1239 Dimethylphthalate 100 6. 5 9 12 39 D ethylphthalate 20 750 10 8 12 39Dimethylphthalate 4 100 900 15 35 60 27 N one-Control Soln 20 300 27Diethylphthalate 7. 5 5 6 8 N one-Control Soln- 2O 13 300 8Diethylphthalate 7. 5 4 5 1 No visible film on solution surface. Thisconcentration is below the limit of solubility of the diethyloxalate inthe ferric chloride solution.

I Composition of Rotogravure grade iron chloride solution.

8 Solution containing antifoamant permitted to stand about 2 weeksbefore t ti 4 Solution containing antitoamant permitted to stand about 6months bei'ore t es t iiig.

' No foam formed.

References Cited in the file of this patent UNITED STATES PATENTS1,969,678 White et al. Aug. 7, 1934 2,045,551 Iddings et a1. June 23,1936 2,101,089 Novak Dec. 7, 1937 2,297,276 Atwood Sept. 29, 19422,382,698 Donlan Aug. 14, 1945 2,430,858 Borsoif et al. Nov. 18, 19472,609,344 Johnson Sept. 2, 1952 2,640,766 Easley et al. June 2, 19532,828,192 Langsfeld Mar. 25, 1958

1. AN AQUEOUS FERRIC CHLORIDE ETCHING SOLUTION CONTAINING A DIESTERMEMBER SELECTED FROM THE GROUP CONSISTING OF DIETHYL PHTHALATE, DIBUTYLPHTHALATE, DIMETHYL PHTHALATE, DIETHYL OXALATE AND DIETHYL FUMARATE,SAID FERRIC CHLORIDE ETCHING SOLUTION CONTAINING FROM ABOUT 5 TO ABOUT45 WEIGHT PERCENT FERRIC CHLORIDE AND THE AMOUNT OF SAID DIESTER MEMBERRANGING FROM ABOUT 2 PARTS PER MILLION UP TO THE SOLUBILITY LIMIT OFSAID MEMBER IN SAID AQUEOUS FERRIC CHLORIDE ETCHING SOLUTION.